arXiv:2610.10309v1 Announce Type: cross Abstract: Conventional wireless communication systems employ antennas with fixed radiation patterns. Enhancing system performance by increasing the number of antennas would push the limits of cost and size for communication devices. To overcome this issue, novel antenna technologies are urgently desired to break through the fundamental performance bottleneck and engineering limits. Pixel antennas provide a general framework for highly reconfigurable antennas, which can flexibly adjust radiation patterns via controlling variable lumped elements placed across adjacent pixels, unlocking novel degrees of freedom (DoF) in the beamspace domain. Recently, an emerging antenna coding technique links wireless system performance to the antenna configurations. This enables the use of pixel antennas to enhance system performance by leveraging the DoF from the antenna side. In this article, we provide a comprehensive overview on antenna coding by pixel antennas. Specifically, based on the pixel antenna model, the concept of antenna coding is firstly introduced, followed by a discussion on the classifications of antenna coding. Two cases for channel gain and multiplexing gain enhancement are highlighted to show the effectiveness of antenna coding in wireless communications. Besides, various optimization approaches for antenna coding design are investigated. Finally, the challenges and opportunities are outlined, providing guidance for future works.